You don't specify your server-side technology stack.
If however you are using Phonegap for the HTML5 App and node.js for the server, you have the option to use:
- node-gcm for sending notifications from your server
- PushPlugin for handling notifications from within your html5 app.
Both are explained at this post:
http://devgirl.org/2013/07/17/tutorial-implement-push-notifications-in-your-phonegap-application/